The invention relates to materials and devices for use with electromagnetic fields and relates in particular to materials and devices through which electromagnetic fields may be propagated in unconventional ways.
For example, the propagation of electromagnetic fields at microwave frequencies through substances with negative values of electrical permittivity and magnetic permeability are disclosed in The Electrodynamics of Substances with Simultaneously Negative Values of ε and μ, by V. G. Veselago, SOVIET PHYSICS USPEKHI, vol. 10, No. 4 (January-February 1968). Such substances are disclosed in this article as having a negative group velocity and are referred to as left-handed substances.
U.S. Patent Application Publication 2001/0038325 discloses a left-handed composite media for use at microwave frequencies in which negative effective electrical permittivity and negative effective magnetic permeability are simultaneously provided. See also, Composite Medium with Simultaneously Negative Permeability and Permittivity, by D. R. Smith, W. J. Padilla, D. C. Vier, S. C. Nemat-Nasser, and S. Schultz, PHYSICAL REVIEW LETTERS, vol. 84, No. 18 (May 2000); Experimental Verification of a Negative Index of Refraction, R. A Shelby, D. R Smith, and S. Schultz, SCIENCE, vol. 292, pp. 77-79 (April 2001); and Loop-Wire Medium for Investigating Plasmons at Microwave Frequencies, by D. R. Smith, D. C. Vier, W. J. Padilla, S. C. Nemat-Nasser, and S. Schultz, APPLIED PHYSICS LETTERS, vol. 75, No. 10 (September 1999).
The use of such devices to achieve negative refraction in a microwave lens is disclosed in Negative Refraction Makes a Perfect Lens, by J. B. Pendry, PHYSICAL REVIEW LETTERS, vol. 85, No. 18 (October 2000). See also, Magnetism from Conductors and Enhanced Nonlinear Phenomena, by J. B. Pendry, A. J. Holden, D. J. Robbins and W. J. Stewart, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. 47, No. 11 (November 1999); and Extremely Low Frequency Plasmas in Metallic Mesostructures, by J. B. Pendry, A. J. Holden, and W. J. Stewart, PHYSICAL REVIEW LETTERS, vol. 76, No. 25 (June 1996).
The above-described materials and devices are disclosed to provide a negative index of refraction for incident radiation at microwave frequencies, and for lowering the plasma frequency in metallic mesostructures into the far infrared and even up to 8.2 GHz band. Such materials, however, are typically limited by the physical size of the metallic components in the structure that provide the negative permittivity and negative permeability under the appropriate radiation frequencies. The size of the components must typically be similar in scale to the wavelength of the excitation field.
A negative index of refraction for incident radiation at the frequency of light has been demonstrated using photonic crystals in Superprism Phenomena in Photonic Crystals, by H. Kosaka, T. Kawashime, A. Tomita, M. Notomi, T. Tamamura, T. Sato and S. Kawakami, PHYSICAL REVIEW B, vol. 58, No. 16 (October 1998). Such materials are disclosed to provide a propagation beam swing of ±90 degrees responsive to a ±12 degrees shift in the angle of incident radiation by modifying the group velocity of the incident radiation. A negative index of refraction has also been demonstrated in the vicinity of the photonic band gap in Theory of Light Propagation in Strongly Modulated Photonic Crystals: Refractionlike Behavior in the Vicinity of the Photonic Band Gap, by M. Notomi, PHYSICAL REVIEW B, vol. 62, No. 16 (October 2000). In particular, this article discloses that negative refraction is possible in regimes of negative group velocity and negative effective index above the first photonic band near the Brillouin zone center (Γ).
Certain applications such as high resolution superlenses, however, may require materials and devices that provide negative refraction at all incident angles for lower frequencies in the photonic band structure. There is further a need for materials and devices that provide negative refraction angles without employing a negative effective index. Additionally, as the above developments have concentrated on two-dimensional materials, there is a further need for three-dimensional materials that provide negative refraction.